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Schematic of an aquifer showing confined zones, groundwater travel times, a spring and a well. An aquifer is an underground layer of water-bearing material, consisting of permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics.
In confined aquifers , the cone of depression is a reduction in the pressure head surrounding the pumped well. When a well is pumped, the water level in the well is lowered. By lowering this water level, a gradient occurs between the water in the surrounding aquifer and the water in the well. Because water flows from high to low water levels or ...
For a confined aquifer or aquitard, storativity is the vertically integrated specific storage value. Specific storage is the volume of water released from one unit volume of the aquifer under one unit decline in head. This is related to both the compressibility of the aquifer and the compressibility of the water itself.
In a confined aquifer, the upper surface of water is overlain by a layer of impervious rock, so the groundwater is stored under pressure. [2] Aquifers receive water through two ways, one from precipitation that flows through the unsaturated zone of the soil profile, and two from lakes and rivers. [2]
The majority of deep aquifers are classified as artesian because the hydraulic head in a confined well is higher than the level of the top of the aquifer. If the hydraulic head in a confined well is higher than the land surface it is a "flowing" artesian well (named after Artois in France). [citation needed]
aquifer – a bed or layer yielding water for wells and springs etc.; an underground geological formation capable of receiving, storing and transmitting large quantities of water. Aquifer types include: confined (sealed and possibly containing “fossil” water); unconfined (capable of receiving inflow); and Artesian (an aquifer in which the ...
An aquifer may be artificially recharged, such as by pumping reclaimed water from wastewater management projects directly into the aquifer. An example of is the Orange County Water District in California. [6] This organization takes wastewater, treats it to a proper level, and then systematically pumps it back into the aquifers for artificial ...
(confined), where S=S s b is the aquifer storativity and = +. (unconfined), where S y is the specific yield of the aquifer. Note that the partial differential equation in the unconfined case is non-linear, whereas it is linear in the confined case. For unconfined steady-state flow, this non-linearity may be removed by expressing the PDE in ...